Unconventional Bottom Paint

[rgranger]

Hey All

I'm hoping for some advice on the use of graphite bottom paint.

I've read a lot about it on a wooden boat forum I belong to but I've never seen it discussed here.

It seems that a lot of the wooden boat people swear by this. They mix a 10% graphite in epoxy and paint it on the bottoms of their boats. The graphite provides UV protection and the slick bottom allows the boats to be dragged over rocks and beached without hurting the bottom much.

Has anyone ever tried this on a fiberglass boat? Seems like it might make sense for a trailer sailor who does not keep his boat in the water for long periods. The slickness might make it easier to keep the bottom clean w/o the use of toxic bottom coats.

Anyone?

 

[Bob McL]

I can see how it might add protection for a wooden boat, but our boats start out with an epoxy bottom, so I don't understand any added value.

 

[Joe]

I guess that's why it's a topic on the wooden boat forum, but not here, out boats already have epoxy on the bottom.

 

[Squidd]

I think he's refering to the graphite, probably a graphite fiber filler, which may or may not add strength, but I don't see how it adds UV protection...

 

[rgranger]

I think he's refering to the graphite, probably a graphite fiber filler, which may or may not add strength, but I don't see how it adds UV protection...

Right Squidd

I'm restoring an older Rhodes 22 and want to put a coat of epoxy paint over the bottom as a barrier coat. The wooden boat folks tote a lot of benefits from putting graphite in the epoxy as a thickener. I've seen it referred to as "Armor Coating" the bottom. And many claim that growth just sluffs off with a little help, the boat slides off the trailer easier, it slides over rocks and sand when beached etc.

Well... I've never actually seen any of these claims first hand but ...it sounds interesting. I just don't want to be the first guy to try it on MY boat, only to find out the hard way why no one with a fiberglass boat does this. One possible reason....I'm guessing that putting a traditional paint over a graphite bottom will no longer be an option as the point of a graphite bottom is that it is slippery. But maybe that is okay. It it works, I'd just start painting with graphite from now on and skip the toxic stuff. And I'm okay with making the commitment to a trailerable boat and not one that will be left in a marina.

And as a chemist, I can see how the layering nature of graphite might impart superior water barrier properties to the coating. (maybe?) And UV protection?... you-betcha! Graphite is just large sheets of fussed benzene rings. Benzene has low lying pi-orbitals capable to absorbing UV-light near 266 nm (give or take a few nanometers) so an extended ring system (like graphite) absorbed considerable UV light. And benzene rings are toxic to many organisms so I can also see how graphite might have some anti-fouling properties... (maybe?)

So if anyone has seen this before, I'd love to hear what you think of it on a fiberglass bottom. Does it adhere well? Does it provide good protection to the bottom? etc.

 

[finding41]

I helped a buddy get out of his transport truck hopper trailer one day. He had gone in to retrieve a shovel or something and got stuck. Too slippery and tall steep sides. The inside was painted with graphite to help the beans or corn or... slide out of the hopper when wet. (It tends to stick inside and the old way of getting it out was to whack the outside of the hopper with a rubber mallet. Some times it took a lot.)
The graphite worked very well.
NOTE: Never get inside or on top of any type of hopper that has any material in it!
As for bottom paint. I'm not convinced I want my boat to be more able to slip off the trailer.

 

[Ken Cross]

been there done that

I think it's an excellence finish for a trailered boat. Don't use it on the topsides because it will absorb sunlight and heat it too much (same reason you don't paint topsides with conventional black paint. As for the bottom it's a bit more slippery (should slide on bunks better) and takes some abuse. It's super easy to apply and to touch up. I have it on the bottom of my drift boat.

I wouldn't use it on my sailboat because it's moored and I don't want to invite critters to take up residence there.

 

[Allan12210]

Right Squidd

And as a chemist, I can see how the layering nature of graphite might impart superior water barrier properties to the coating. (maybe?) And UV protection?... you-betcha! Graphite is just large sheets of fussed benzene rings. Benzene has low lying pi-orbitals capable to absorbing UV-light near 266 nm (give or take a few nanometers) so an extended ring system (like graphite) absorbed considerable UV light. And benzene rings are toxic to many organisms so I can also see how graphite might have some anti-fouling properties... (maybe?)

So if anyone has seen this before, I'd love to hear what you think of it on a fiberglass bottom. Does it adhere well? Does it provide good protection to the bottom? etc.

Benzene has hydrogen in it (sp3 hybridization). Graphite is pure carbon, just like diamond only a different crystal structure. Not particularly toxic. It has lubricity because the layers are only loosely bonded. It is probably so incompatable with epoxy that it is just sloughing off as the boat is being dragged around the beach. It would be nice if the marine growth wouldn't stick to it. I'm pretty sure thats been tried along with molybdinum sulfide and Teflon. They still seem to stick.

 

[rgranger]

Benzene has hydrogen in it (sp3 hybridization). Graphite is pure carbon, just like diamond only a different crystal structure. Not particularly toxic. It has lubricity because the layers are only loosely bonded. It is probably so incompatable with epoxy that it is just sloughing off as the boat is being dragged around the beach. It would be nice if the marine growth wouldn't stick to it. I'm pretty sure thats been tried along with molybdinum sulfide and Teflon. They still seem to stick.

You are right about benzene having hydrogens.. but both benzene and graphite are sp2

My wonderings are along the lines of what happens when marine growth attempts to bond to (and break down) the graphite... would benzene like molecules be released. As far as bonding to epoxy... from what I've read it works great (on the wooden boats) but I have not seen anyone try it on a fiberglass boat.

 

[JVB]

There are less expensive ways to make it easy for a boat to slip off a trailer. Just spray silicone lubricant on the trailer bunks. But keep a bow line tied until you reach the unloading position or your water scooter may slip off prematurely and "whang" the transom on the concrete ramp. Don't ask how I know that !

 

[Allan12210]

.. but both benzene and graphite are sp2

.

Oops, you caught me on that one.:cussing: Might be worth a try...mix up a bit of graphite in epoxy (maybe 20 volume percent) and coat it on a piece of PC board (without the copper layer). Hang that coupon over the back of the boat for a while and see what happens. I dug around the garage and can't find any graphite...just a bottle of MoS2 and some microfine teflon powder.

The benzene thing might not be so attractive for the environmentalists with the leukemia and all. I remember when I first started working, I was using tons of that stuff to azeotrope off the water in things we made in the lab.

 

[Ken Cross]

I got my graphite powder here

go to the Store on this website. You will find West System 423 Graphite powder.
And it supports this site. They deliver fast.

 

[rgranger]

go to the Store on this website. You will find West System 423 Graphite powder.
And it supports this site. They deliver fast.

Thanks Ken: If I go this route, I'll definitely buy here. I'm still hoping to hear from someone who tried it and loved it.

 

[rgranger]

The benzene thing might not be so attractive for the environmentalists with the leukemia and all. I remember when I first started working, I was using tons of that stuff to azeotrope off the water in things we made in the lab.

Well I don't think it would release benzene to the environment directly... but it might be converted to benzene through the metabolism of the growth....

speculation but interesting to think about.


And yes.... when I was an undergraduate student, we washed all of our glassware in benzene.

Wish I could say it had no effect but truth is... I wear a survivor's T-shirt at Relay for Life.

Who knows for sure... I play it as safe as I can now. And that is partially the reason I'm looking at this bottom system. I don't want to work with toxic paints that contain biocides and other stuff if something simple like graphite will provide the protection I need. As a trailer sailor, I don't need as much bottom protection as others.

I'm also wondering if I am over thinking this. The boat I'm sailing at present has a bottom coat that is simply rustoleum enamel paint and I have never had to do more than pressure wash the bottom as soon as I haul her out. I use the high gloss paint so the bottom is very smooth. I never leave her in the water more than a week at a time so growth is minimal (just the beginnings of a green slime). I do have ambitions of taking some two week to four week cruises in the future so... ??? maybe I need a better bottom system.

Maybe I should just put a barrier coat on this boat, then repeat with rustoleum to protect the epoxy from UV and worry about this down the road IF a problem develops.

 

[Bob McL]

POR 15 is so slick no other paint can stick to it unless a special primer is used. When I used it on my keel, I had a little left so I coated inside the keel trunk and around the trunk. The paint I applied over that area came off in sheets about 8x10-inches. Pretty slick.

 

[shemandr]

I have used the West Graphite additive with epoxy on the plywood bottom of my dink - especially since I have both on hand and don't always want to spring for a can of bottom paint It works pretty well It does stand up to dragging on the beach It is easy to apply It does need recoating - probably becuase of the sun on it in the off season You can sand it and use bottom paint over it My dink is in all season The growth on the bottom is reduced but not eliminated I still give it a scrub when I do the bottom of Artemis - about every two weeks It hasn't worked well enough for me to consider putting on the bottom of the keel boat

 

[Allan12210]

Wish I could say it had no effect but truth is... I wear a survivor's T-shirt at Relay for Life.
.

Relay for Life is tomorrow around here. My sister has the same t-shirt. We never knew what the long term effects might be for the stuff we handled. So far so good and now my wife (she's a chemist too) and I make sure we use the proper protection when working with solvents, paint and resins.

After your barrier coat, try a good coat of wax too.

Stay well.

 

[robertsapp]

I'm still trying to figure out why I would be worried about UV protection for the underside of my boat. That's usually the part that's underwater. If it's not, I have bigger concerns than a boat bottom sunburn.

If graphite turns out to be a good material for bottom coating, I'm sure Friends Of The Barnacles will file suit and some EPA bureacrat will ban its use.

 

[rgranger]

I'm still trying to figure out why I would be worried about UV protection for the underside of my boat. That's usually the part that's underwater. If it's not, I have bigger concerns than a boat bottom sunburn

True nuff....

but I'm a trailer sailor so... my boat sits out of the water all but about 20 days out of the year.